Fatigue Properties of Hemp and Glass Fiber Composites

The fatigue properties of nonwoven randomly oriented short hemp fiber mat and chopped strand mat (CSM) glass fiber reinforced polyester composites have been studied, mainly in tension-tension mode. Despite having poorer absolute fatigue strength, the hemp fiber composites exhibited less fatigue sensitivity as compared with the CSM glass fiber composites in tension-tension fatigue. This could be correlated with the lower stiffness degradation observed during fatigue of the hemp fiber composites as compared with the glass fiber composites at the same normalized peak stress levels. Also, images recorded during fatigue loading showed that the hemp fiber composites were better at resisting crack formation and growth than the glass fiber composites. These results suggest that hemp fiber composites have the potential to replace glass fiber composites in applications where components are subjected to fatigue loads but the stress levels are of moderate value. (C) 2014 Society of Plastics Engineers